Aflatoxins are toxins produced by Aspergillus species that grow on several crops, in particular on peanuts, maize or corn before and after harvest of the crop as well as during storage. The biosynthesis of aflatoxins involves a complex polylcetide pathway starting with acetate and malonate. One important intermediate is sterigmatocystin and O-methylsterigmatocystin which are direct precursors of aflatoxins. Important producers of aflatoxins are Aspergillus flavus, most strains of Aspergillus parasiticus, Aspergillus nomius, Aspergillus bombycis, Aspergillus pseudotamarii, Aspergillus ochraceoroseus, Aspergillus rambelli, Emericella astellata, Emericella venezuelensis, Bipolaris spp., Chaetomium spp., Farrowia spp., and Monocillium spp., in particular Aspergillus flavus and Aspergillus parasiticus (Plant Breeding (1999), 118, pp 1-16). There are also additional Aspergillus species known. The group of aflatoxins consists of more than 20 different toxins, in particular aflatoxin B1, B2, G1 and G2, cyclopiazonic acid (CPA).
The protection of crops from aflatoxins that contaminate crop grains is a constantly recurring problem in agriculture, horticulture and other plant cultivation practices. To help combat this problem, it has been discovered that certain isolated non-toxigenic Aspergillus strains which occur naturally in agricultural fields have been found effective in preventing aflatoxin contamination by competitively excluding the toxigenic strains.
For certain agricultural, horticultural, and other related applications it is often desirable to formulate biocontrols as dry spreadable or broadcast granules that are applied using a granular spreader, whereas for other use patterns such materials are suitably formulated as wettable powders or water dispersible granules (WDGs) that are designed for admixing in large volumes of water such as tank mixes and ultimately applied as a foliar spray suspended in water. The challenge to deliver biologically stable products for these two approaches can be different.
U.S. Pat. No. 6,027,724 refers to compositions comprising non-toxigenic strains of Aspergillus that are cultured as single strains on granular food sources, such as for example rice, rye, etc.; or incorporated into extruded food matrices, such as for example wheat gluten-kaolin matrices.
US patent application publication 20090060965 refers to a water dispersible granule formulation containing non-toxigenic strains of Aspergillus; a binding agent; an agent having osmoprotectant and adhesive properties; a carrier agent, and a nutrient source. The WDG can be dispersed in water and applied as a sprayable conidial suspension for the prevention of aflatoxin contamination in food.
There is a continued need to develop water dispersible granule formulation containing non-toxigenic strains of Aspergillus having improved stability during processing and on long term storage.